This invention relates to a fluorescent display tube and a method of driving the same.
Generally, in a fluorescent display tube, electrons emitted by a filament shaped cathode are caused to collide against an anode coated with a phosphor layer for exciting the phosphor layer to emit light thus displaying a character, pattern, digit or the like.
For this reason, in most prior art constructions, a mesh shaped grid is interposed between the cathode and anode for the purpose of accelerating electrons emitted from the cathode. Such display tube is constructed such that the luminous display of the anode can be viewed through the mesh shaped grid.
For this reason, it has been necessary to construct the grid such that it can provide a control function for controlling and accelerating the electrons emitted by the cathode and collided upon the anode and that it would have a thin and fine mesh construction to enable viewing from outside the luminous characters or the like displayed by the anode. Furthermore, an ordinary fluorescent display tube is provided with digits or characters of a plurality of orders of magnitude and for the purpose of imparting an adequate mechanical strength to the grids, a frame of a definite width is provided, and respective grids are spaced from each other enabling a viewer to see the displayed matters through the spacings. However, where the grids are arranged in a manner as above described, that is covering each unit display segment group and not to cover portions between displayed matters, it is necessary to separate adjacent display segment groups a definite distance. Moreover, where grids of complicate shape are divided there are many problems.
Where the grids are spaced in the longitudinal direction of the tube, the presence of laterally long displayed matters makes it more difficult to construct the grids.
To provide a display which perfectly surround a displayed matter is nearly impossible.